var details = ["7868190130M7522","5303914400F9211","9273338290F4010"]
var countSeniors = function(details) {
    let count = 0;
    for (var i = 0;i<details.length;i++){

        if(details[i].slice(11,13)>60){
            count++
        }
    }
    return count
}
console.log(countSeniors(details));

